In the field of medical technology various systems are known with which fluids may be removed from a patient or fluids may be supplied to a patient via tubing. In general access to the patients is with a catheter for inserting into body organs or with a cannula for puncturing blood vessels. During the examination or treatment proper access to the patient must be assured. Therefore it is necessary to monitor the patient access.
Extracorporeal blood treatment devices that involve in particular extracorporeal blood flow also require a proper access to the patient. Among known extracorporeal blood treatment devices are for instance dialysis systems and cell separators that require an access to the patient's vascular system. During extracorporeal blood treatment, blood is removed from the patient via arterial tubing with an arterial puncture cannula, and the blood is resupplied to the patient via venous tubing with a venous puncture cannula. During acute dialysis at intensive care stations, a central venous catheter is inserted in the neck or leg of the patient to create the vascular access. In the field of chronic dialysis, between 20% and 40% of patients have a catheter as a temporary or permanent vascular access.
In general luer connection systems are used for connecting and attaching tubing in the field of medicine; their connecting parts include an internal taper and an external taper. These connection systems are called luer lock connectors when the internal taper and external taper also include a thread for securing the connection. Although the luer lock connectors offer a very high level of reliability, in practice it has been found that when handled improperly, if there are material defects, or when used too frequently the connecting parts can detach from one another or microtears can occur in the material. US 2010/0228231 therefore suggests securing the connecting parts of a luer lock connector against unintentional detachment using an additional fixation of the connecting parts.
Various devices having different designs known for detecting blood escaping in general make use of the safety devices normally present in blood treatment devices; these initiate an immediate interruption in the extracorporeal blood flow if the vascular access is not in proper order.
Devices for detecting blood escaping at a puncture site are known that are embodied as a pad that comprises an absorbent material in which a moisture sensor is embedded. Such pads are known for instance from WO 2006/008866 A1, US 2005/0038325 A1 and U.S. Pat. No. 6,445,304 B1.
WO 99/24145 describes a device for detecting blood that has a rigid housing that can be closed with a cover and in which is arranged a moisture sensor. Passages are provided in the housing for feeding through the cannulas and tubing. It is a drawback that the housing with the moisture sensor is relatively costly to produce in large numbers and in practice is relatively difficult to handle. In addition, it is not possible to conduct a visual control because the sensors are positioned against the walls of the two halves of the housing.